9.3 Thermoregulation

What is thermoregulation?

• regulation of internal body temperature

• controlled by negative feedback mechanisms

• helps maintain a stable set point depending on the species

How does thermoregulation work?

• Detects changes in internal or external temperature

• Activates responses to return temperature to the set point

• Maintains homeostasis

What is conduction?

• Transfer of thermal energy through direct contact between molecules

• Heat moves from warmer to cooler objects touching each other

What is convection?

• Transfer of thermal energy through fluids (liquids or gases)

• Warm fluid rises, cool fluid sinks, creating movement of heat

What is radiation?

• Transfer of thermal energy through electromagnetic waves

• Does not require direct contact or a medium

What is evaporation in thermoregulation?

• Water (like sweat) changes into vapour from the skin

• Absorbs heat energy from the body

• Causes cooling

How do animals exchange thermal energy?

• Through conduction, convection, radiation, and evaporation

• All animals use some combination of these methods to regulate temperature

What is a homeotherm?

An animal that maintains a stable body temperature despite changes in the external environment

What are examples of homeotherms?

• Birds

• Mammals

What is a poikilotherm?

• An animal whose body temperature varies with the external environment

• Body temperature often matches the surrounding temperature

What are examples of poikilotherms?

• Fish

• Reptiles

• Amphibians

• Most invertebrates

What is the main difference between homeotherms and poikilotherms?

• Homeotherms maintain a relatively constant body temperature

• Poikilotherms have body temperatures that change with the environment

What is an endotherm?

• An animal that maintains its body temperature using internal mechanisms

• Warm-blooded

What are examples of endotherms?

• Mammals

• Birds

What internal mechanisms do endotherms use to regulate temperature?

• Sweating

• Shivering

• Vasodilation

• Vasoconstriction

Can endotherms maintain a constant body temperature regardless of their surroundings?

• Yes

• They regulate their temperature internally

What is the role of the hypothalamus in endotherms?

• Coordinates responses that regulate body temperature

• Acts as the integrator in thermoregulation

How much of an endotherm's energy from food is used to maintain body temperature?

• About 80%

Why are endotherms more successful at maintaining a stable body temperature than ectotherms?

• They generate and regulate heat internally

• They are less dependent on environmental temperatures

What is an ectotherm?

• An animal that maintains its body temperature by absorbing heat from the environment

• Cold-blooded

What are examples of ectotherms?

• Invertebrates

• Most fish

• Amphibians

• Reptiles

How do ectotherms regulate their body temperature?

• By gaining or losing heat from their surroundings

• Depend on environmental temperatures

Why do ectotherms have lower energy requirements than endotherms?

• They do not use food to generate body heat

• They rely on external heat sources instead

What is the main difference between endotherms and ectotherms?

• Endotherms use internal mechanisms to control body temperature

• Ectotherms rely on heat from the environment to control body temperature

Why can endotherms remain active over a wider range of temperatures than ectotherms?

• They generate and regulate heat internally

• They are less dependent on environmental temperatures

What happens to some of the energy from glucose in endotherms?

• It is converted into thermal energy (heat)

• Helps maintain body temperature

What are thermoreceptors?

• Receptors that detect changes in temperature

• Found in the skin and inside the body

What is the role of thermoreceptors?

• Alert the nervous system to changes in internal or external temperature

• Trigger responses to maintain homeostasis

Why do aquatic invertebrates have poor thermoregulatory abilities?

• Their body temperature closely matches the temperature of their environment

• They have limited control over body temperature

How do amphibians and lizards regulate body temperature?

• Through conduction and radiation

• Gain or lose heat from their surroundings

How does a lizard regulate its body temperature?

• Basks on a sunny rock to warm up

• Moves to a cooler location when it gets too hot

What is thermal acclimatization?

The process by which an animal gradually adjusts to temperature changes in its environment

What happens when an endotherm's body temperature drops below the set point?

• Blood vessels near the skin constrict (vasoconstriction)

• Reduces heat loss to the environment

• Shivering begins to generate heat

• Goose bumps occur and hairs stand up to help maintain warmth

Why does shivering help regulate body temperature?

Rapid muscle contractions generate thermal energy (heat)

Why do hairs stand up when the body is cold?

• Helps trap a layer of air near the skin

• Reduces heat loss and helps maintain warmth

What happens when an endotherm's body temperature rises above the set point?

• Blood vessels near the skin relax and widen (vasodilation)

• More heat is released through the skin

How does sweating help cool the body?

• Sweat is released onto the skin

• As it evaporates, it absorbs thermal energy

• This cools the body

What are the main responses to cold temperatures in endotherms?

• Vasoconstriction

• Shivering

• Goose bumps/hairs standing up

What are the main responses to hot temperatures in endotherms?

• Vasodilation

• Sweating

What is hypothermia?

A condition in which core body temperature falls below the normal range

What can happen if body temperature drops by a few degrees?

• Coma

• Possible death

Can people survive prolonged periods of hypothermia?

• Yes, some individuals, especially children, have survived prolonged hypothermia

What is the diving reflex?

• A response triggered by cold water submersion

• Heart rate slows down

• Blood is redirected to the brain and other vital organs

• Helps conserve heat and increase chances of survival in cold water